The term “vehicle” refers to common automobiles but also elevator trucks, earth-moving vehicles, off-road and non-off-road telescopic trucks, military vehicles, tractors, air platforms, i.e. all vehicles which, during their normal use, effect maneuvers in which the relative wheels have a steering configuration necessary for allowing a movement, for example straight or curved, of the vehicle itself.
In currently known vehicles, the steering, i.e. the positioning of a particular desired orientation of at least one pair of wheels, is generally controlled mechanically by means of a rack coupling activated by the movement of the steering wheel or hydraulically by means of a hydraulic auxiliary system again controlled by the rotation of the steering wheel.
In particular, the known steering groups act on the wheels of an axle which are constrained to the vehicle by means of structural extensions.
In order to effect a turn, when desired, the presence is currently envisaged of a rigid rod element connected at one end to a steering stem by means of a spherical coupling and at the other end to the wheel-holder group by means of a pin, this being the construction solution of the integrated steering cylinder type mainly used for axles to be installed on off-road vehicles.
At present, therefore, in order to effect a sudden turn, a user exerts a translatory movement, generally, as already mentioned, by means of the steering wheel, to the above stem of the main cylinder which in turn entrains the other rigid rod element situated in series with the previous stem, into movement.
As this rigid rod element, however, is integrally hinged to the wheel-holder supports of the wheels of a common axle, the latter are concordantly put into movement around respective kingpins through which they are rotatingly connected to the structural extensions. Consequently, the rigid rod elements constrain the wheel-holder supports to rotating in the same direction in response to movement of the steering stem.
The only turns therefore that a current known vehicle can make through the coupling described above falls within the typologies contemplated by the “Ackermann”-type geometry in which the axes of the steering wheels of a vehicle intersect upon a single point along a line extending from a rear axle of the vehicle when the steering wheels are rotated from a straight advance position.
Unfortunately, however, these known groups have various drawbacks and impose kinematic limits to the vehicle itself on which they are assembled.
In particular they relate to the limited angular deviation of the wheel-holder support as a result of the limited translatory movement of the steering stem.
In other words, unfortunately, the angular deviation of the wheel-holder group around the kingpin is limited within a narrow angular range which cannot exceed what is granted by the translatory movement of the steering stem. Unfortunately the steering mechanism in accordance with Ackermann steering geometry does not allow rotation of the vehicle with respect to a point inside the ground-support quadrilateral of the vehicle.
It is not possible, for example, for present known vehicles to rotate around a center of a non-steering axle, for example, nor is it possible to effect a rotation with respect to the center of the vehicle itself for the above-mentioned kinematic reasons of the known steering mechanisms in accordance with Ackermann steering geometry and also because it is not possible for current known vehicles to impose two opposing rotations on a pair of driving wheels of the same axle.